Members of the family of integral membrane proteins referred to as the ABC (ATP binding cassette) membrane proteins have been shown to us by function as ATP channels in some of our recent investigations. In particular MDR (multidrug resistance), responsible for drug resistance in cancer, and CFTR (cystic fibrosis transmembrane conductance regulator), the protein which when mutated leads to the genetic disease Cystic Fibrosis, are important members of this family. They both function as ATP channels transporting intracellular ATP to the cell surface and extracellular space. We have ongoing studies that define further membranes of this ATP transporting family to include the MRP (multidrug resistance-associated protein), responsible for some non-MDR drug resistance in cancer and SUR (sulfonyl urea receptor) responsible for triggering release of insulin.